Abstract The objective of this research is to undertake a detailed analysis of an under-investigated class of proteins: the mammalian phosphatidylinositol/phosphatidylcholine transfer proteins (PITPs). The functions and mechanisms of function of PITPs in mammalian cells remain to be elucidated. The research plan is designed to identify mechanisms of function of specific mammalian PITP isoforms [unreadable] the Class 1 PITPs. This proposal is founded on our creation and characterization of a PITP&#945;knockout mouse. In that regard, it extends the studies we have already performed in that context. The Pitp&#945;0/0 mouse is an ideal disease model in that it is born alive, but manifests powerful phenotypes after birth. Using this unique model as primary analytical subject, we will undertake three lines of investigation. First, we will use sophisticated and quantitative imaging and image reconstruction assays to test how the Class 1 PITP&#945;plays genuine, and important, roles in brain neurodevelopment [unreadable] specifically in cellautonomous and cell-nonautonomous roles in axon pathfinding. Questions of how this protein regulates both signal reception and signal instruction will be addressed using high resolution imaging, axon guidance, and biochemical assays. Second, we will address the biochemical properties of highly related Class 1 PITPs that serve as functional bar codes that specify the activities of these proteins in cells. Further, we will dissect the various biochemical properties of the two featured Class 1 PITPs (PITP&#945;and PITP&#945;) and assign the contribution of each to physiological function. A prime focus will be placed on the relationship between Class 1 PITP activity and regulation of phosphoinositide synthesis. Third, we will use sophisticated biochemical and computational approaches to decipher how Class 1 PITPs function at the level of single molecules. It is not a large exaggeration to describe these analyses as operating at atomic-level resolution. PITPs play central roles in regulating signal transduction pathways that interface with diverse cellular processes. We now extend our analyses of these proteins to neurodevelopmental questions associated with mechanisms associated with pathfinding by thalamocortical axons, and high resolution dynamics analyses that probe how these proteins work at the level of single molecules. The Bankaitis laboratory is uniquely poised to address questions of mechanism of PITP&#945;(and Class 1 PITP) function as it has developed unique experimental systems for analysis.